Amazon on Wednesday said it has delivered its first Prime Air order, an important milestone after revealing its drones program three years ago. Last week, one of the company's drones dropped off an Amazon Fire TV and bag of popcorn in the backyard of a customer near Cambridge, England -- 13 minutes after the customer ordered it online.

Delivery drones could become Amazon's next step in getting us what we need faster and with lower shipping costs. With Amazon hoping to roll them out worldwide, these vehicles have the potential to significantly change the way we shop. Walmart, UPS and Google parent Alphabet are also testing out delivery drones. For instance, Alphabet started a pilot program that delivers Chipotle burritos on the campus of Virginia Tech.

Yet these unmanned aircraft still need to clear extensive regulatory and safety hurdles before they reach the mainstream -- if they ever do. In the US, the Federal Aviation Administration has, for now, essentially banned delivery drones, since these vehicles need to be in the line of sight of an operator to fly legally. More regulations around drones are still being developed, but that could take years.

The UK program, still in a private beta, aims to drop off a package in 30 minutes or less after you place an order. Customers can order from thousands of items seven days a week during daylight hours, weather permitting.

The project has started with just two customers in the UK, but Amazon plans to expand participation to dozens of customers living several miles from its UK facility and hopes to eventually expand to hundreds more. At least for the private test phase, these customers won't have to pay any additional shipping costs; no word on whether that could change as the program grows.

The autonomous drones can carry packages up to five pounds, and they're guided by GPS. Obviously, the service will only be available for certain items.

Amazon's pilot program comes after the company in July got permission from the UK government to test delivery drones there. It was approved to evaluate drones in three main areas: flights beyond line of sight in rural and suburban areas; tests of sense-and-avoidance systems; and operations by one person of multiple drones.